Polishing apparatus and polishing method

ABSTRACT

A polishing apparatus polishing a surface of a substrate, such as a semiconductor substrate. The polishing apparatus including a substrate holding mechanism, a polishing table having a polishing surface, and a polishing surface temperature controller for controlling a temperature distribution of the polishing surface. The substrate holding mechanism and the polishing table provide relative movement between the surface of the substrate and the polishing surface while the substrate holding mechanism presses the surface of the substrate against the polishing surface to thereby polish the surface of the substrate. The polishing surface temperature controller controls the temperature distribution so that the polishing surface has a predetermined temperature distribution to thereby control removal rates of portions of the surface of the substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus and a polishing method for polishing a substrate, such as a semiconductor substrate, by operating a substrate holding mechanism so as to bring the substrate into contact with a polishing surface of a polishing table and by providing relative movement between a surface of the substrate and the polishing surface.

2. Description of the Related Art

A chemical mechanical polishing (CMP) apparatus has been known as an apparatus for polishing a substrate, e.g., a semiconductor substrate. This type of polishing apparatus includes a polishing table, a polishing cloth (polishing pad), and a substrate holding mechanism (top ring) for holding a substrate. The polishing cloth is attached to an upper surface of the polishing table to form a polishing surface. A substrate to be polished (hereinafter referred to as a substrate), such as a semiconductor substrate, is pressed against the polishing surface by the substrate holding mechanism while a polishing liquid is supplied onto the polishing surface. The polishing table and the top ring are rotated to provide relative movement between the substrate and the polishing surface to thereby polish a surface of the substrate to a flat and mirror finish.

In an approach to a fine semiconductor device, it is important to uniformly polish the surface of the substrate using the above CMP apparatus. Thus, there has been proposed to optimize a pressure distribution within the surface of the substrate by adjusting contact pressure acting between the surface of the substrate and the polishing surface so as to uniformly polish the surface of the substrate, as shown in Japanese laid-open patent application No. 2002-86347.

However, a polishing rate (removal rate) of the surface of the substrate is affected not only by contact pressure acting between the substrate and the polishing surface, but also by a temperature of the polishing surface, a concentration of the polishing liquid (i.e., slurry) to be supplied, and the like. Accordingly, adjustment of the contact pressure is not enough to completely control the removal rate. Particularly, in a CMP process in which a removal rate greatly depends on a temperature of the polishing surface (for example, in a case where a surface hardness of a polishing cloth greatly depends on a temperature thereof), the removal rate would vary from area to area of the surface of the substrate depending on a temperature distribution, and as a result, a uniform polishing profile cannot be obtained. Generally, the temperature distribution of the polishing surface is not uniform, and there are temperature differences between areas within the polishing surface. The non-uniform distribution and temperature differences are a result of several causes, including heat generated from the polishing surface itself due to contact with a retainer ring provided on the top ring for holding the substrate, non-uniform heat absorptivity of the polishing surface, and current directions of the slurry supplied to the polishing surface.

Further, in the above-mentioned CMP process in which the removal rate greatly depends on the temperature of the polishing surface, the removal rate is proportional to contact pressure acting between the polishing surface and the substrate, so long as the contact pressure is within a certain range. However, when the contact pressure is beyond the above range, the removal rate does not vary even if the contact pressure is changed. In this case, when the surface of the substrate has an area where a temperature thereof is different from those of other areas, the removal rate of such an area cannot be changed with a local change in contact pressure applied to this area. As a result, non-uniformity of the removal rate within the surface cannot be resolved. That is, only adjustment of the contact pressure cannot provide a uniform polishing profile of the surface in its entirety.

If the contact pressure between the entire surface of the substrate and the polishing surface is lowered, it is possible to suppress an increase in temperature of the polishing surface and thus to improve controllability of the polishing profile by changing the contact pressure. However, the removal rate of the surface of the substrate is lowered in its entirety, and hence productivity is decreased. Thus, it is difficult to obtain a uniform polishing profile while maintaining a high removal rate.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a polishing apparatus and a polishing method which can obtain a uniform polishing profile while keeping a high removal rate even in a CMP process in which a removal rate greatly depends on a temperature of a polishing surface.

In order to solve the above drawbacks, one aspect of the present invention provides a polishing apparatus comprising a substrate holding mechanism for holding a substrate, a polishing table having a polishing surface, and a polishing surface temperature controller for controlling a temperature distribution of the polishing surface. The substrate holding mechanism and the polishing table are operable to provide relative movement between the surface of the substrate and the polishing surface while the substrate holding mechanism presses the surface of the substrate against the polishing surface to thereby polish the surface of the substrate. The polishing surface temperature controller controls the temperature distribution so that the polishing surface has a predetermined temperature distribution to thereby control removal rates of portions of the surface of the substrate.

According to the present invention described above, even in a CMP process in which the removal rate greatly depends on the temperature of the polishing surface, the removal rates of the portions of the surface can be controlled as desired without lowering pressure applied to the surface of the substrate in its entirety. As a result, a uniform polishing profile can be obtained while maintaining a high removal rate of the surface of the substrate.

In a preferred aspect of the present invention, the polishing surface temperature controller comprises a fluid ejection mechanism for providing the predetermined temperature distribution on the polishing surface by ejecting a fluid to the polishing surface.

According to the present invention described above, a desired temperature distribution can be obtained with a simple structure, and a uniform polishing profile can be obtained.

In a preferred aspect of the present invention, the fluid ejection mechanism comprises plural fluid ejection ports.

According to the present invention described above, the fluid ejection mechanism can divide the polishing surface into small zones, and can control the temperature distribution, i.e., temperatures of the respective zones as desired. Therefore, a more uniform polishing profile can be easily obtained.

In a preferred aspect of the present invention, the polishing apparatus further comprises at least one of a flow rate controller and a temperature controller. The flow rate controller is for individually adjusting flow rates of the fluid to be ejected through the plural fluid ejection ports, and the temperature controller is for individually adjusting temperatures of the fluid to be ejected through the plural fluid ejection ports.

According to the present invention described above, local portions of the polishing surface can be provided with a desired temperature distribution, and hence a more uniform polishing profile can be easily obtained.

In a preferred aspect of the present invention, the polishing apparatus further comprises at least one of an ejection port number adjuster and a supply position adjuster. The ejection port number adjuster is for adjusting the number of fluid ejection ports to be used for ejecting the fluid, and the supply position adjuster is for adjusting supply positions where the ejected fluid from the fluid ejection ports strikes the polishing surface.

According to the present invention described above, local portions of the polishing surface can be provided with a desired temperature distribution, and hence a more uniform polishing profile can be easily obtained.

In a preferred aspect of the present invention, the polishing apparatus further comprises a temperature-distribution measuring device for measuring the temperature distribution of the polishing surface. Based on a measurement result of the temperature-distribution measuring device, the polishing surface temperature controller controls ejection of the fluid using at least one of the flow rate controller and the temperature controller to thereby provide the predetermined temperature distribution on the polishing surface.

In a preferred aspect of the present invention, the polishing apparatus further comprises a temperature-distribution measuring device for measuring the temperature distribution of the polishing surface. Based on a measurement result of the temperature-distribution measuring device, the polishing surface temperature controller controls ejection of the fluid using at least one of the ejection port number adjuster and the supply position adjuster to thereby provide the predetermined temperature distribution on the polishing surface.

According to the present invention described above, a desired temperature distribution of the polishing surface can be accurately provided based on an actual temperature distribution of the polishing surface, and hence a more uniform polishing profile can be obtained.

Another aspect of the present invention is to provide a polishing method comprising bringing a surface of a substrate into contact with a polishing surface, providing relative movement between the surface of the substrate and the polishing surface to perform polishing of the surface of the substrate, and during the polishing, controlling a temperature distribution of the polishing surface so that the polishing surface has a predetermined temperature distribution to thereby control removal rates of portions of the surface of the substrate.

According to the present invention described above, even in a CMP process in which the removal rate greatly depends on the temperature of the polishing surface, the removal rates of the portions of the surface can be controlled as desired without lowering pressure applied to the surface of the substrate in its entirety. As a result, a uniform polishing profile can be obtained while maintaining a high removal rate of the surface of the substrate.

Another aspect of the present invention is to provide a polishing method comprising bringing a surface of a substrate into contact with a polishing surface, and providing relative movement between the surface of the substrate and the polishing surface to perform polishing of the surface of the substrate. The polishing includes performing a first polishing process of polishing the surface of the substrate while controlling a temperature distribution of the polishing surface so that the polishing surface has a predetermined temperature distribution, and performing a second polishing process of polishing the surface of the substrate without controlling the temperature distribution of the polishing surface.

According to the present invention described above, on one hand, a uniform polishing profile can be obtained by controlling the temperature distribution of the polishing surface in the first polishing process. On the other hand, in the second polishing process, polishing can be performed while preventing problems including drying of the polishing surface which would be caused by controlling of the temperature distribution of the polishing surface.

In a preferred aspect of the present invention, the first polishing process comprises performing polishing while ejecting a fluid to the polishing surface so as to control the temperature distribution of the polishing surface, and the second polishing process comprises performing polishing without ejecting the fluid to the polishing surface.

According to the present invention described above, drying of the polishing surface can be prevented during the second polishing process. As a result, aggregation of polishing particles can be prevented, and defects, such as scratching, of the surface of the substrate can be prevented.

Another aspect of the present invention is to provide a polishing method comprising bringing a surface of a substrate into contact with a polishing surface, and providing relative movement between the surface of the substrate and the polishing surface to perform polishing of the surface of the substrate. The polishing includes performing a first polishing process of polishing the surface of the substrate while controlling a temperature distribution of the polishing surface so that the polishing surface has a predetermined temperature distribution, and performing a second polishing process of polishing the surface of the substrate while maintaining a higher temperature distribution of the polishing surface than that during the first polishing process.

According to the present invention described above, the removal rate during the second polishing process is lower than that during the first polishing process. As a result, the polishing end point can be accurately detected in the second polishing process, and hence the polishing end point detection can be improved.

In a preferred aspect of the present invention, the first polishing process comprises performing polishing while ejecting a fluid to the polishing surface at a predetermined flow rate, and the second polishing process comprises performing polishing while ejecting the fluid to the polishing surface at a lower flow rate than that during the first polishing process.

According to the present invention described above, as a result a simple change of process conditions, the removal rate during the second polishing process becomes lower than that during the first polishing process, and hence the polishing end point can be accurately detected in the second polishing process. Further, drying of the polishing surface can be prevented during the second polishing process.

Another aspect of the present invention is to provide a polishing method comprising bringing a surface of a substrate into contact with a polishing surface, and providing relative movement between the surface of the substrate and the polishing surface to perform polishing of the surface of the substrate. The polishing process includes performing a first polishing process of polishing the surface of the substrate while ejecting a non-humidified gas to the polishing surface so that the polishing surface has a predetermined temperature distribution, and performing a second polishing process of polishing the surface of the substrate while ejecting a humidified gas to the polishing surface so that the polishing surface has a predetermined temperature distribution.

According to the present invention described above, drying of the polishing surface can be prevented during the second polishing process. As a result, aggregation of polishing particles can be prevented, and defects, such as scratching, of the polishing surface can be prevented.

In a preferred aspect of the present invention, a time of the first polishing process accounts for more than half of an entire time of the polishing.

According to the present invention described above, polishing can be performed without lowering the removal rate other than around a polishing end point.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view showing a structure of a polishing apparatus according to a first embodiment of the present invention;

FIGS. 2A and 2B are views illustrating a structure of a fluid ejection mechanism 30, FIG. 2A being a view showing a polishing table as viewed from above, FIG. 2B being a view showing the polishing table as viewed from a lateral direction;

FIG. 3 is a view showing a whole structure of the fluid ejection mechanism 30;

FIGS. 4A and 4B are views illustrating a structure of a fluid ejection mechanism 30-2 incorporated in the polishing apparatus according to a second embodiment, FIG. 4A being a view showing a polishing table as viewed from above, FIG. 4B being a view showing the polishing table as viewed from a lateral direction;

FIG. 5 is a view showing a whole structure of the fluid ejection mechanism 30-2;

FIGS. 6A and 6B are views illustrating a structure of the polishing apparatus according to a third embodiment of the present invention, FIG. 6A being a view showing a polishing table as viewed from above, FIG. 6B being a view showing the polishing table as viewed from a lateral direction; and

FIGS. 7A and 7B are views illustrating an example of the present invention, FIG. 7A being a view showing the polishing table as viewed from above, FIG. 7B being a graph showing a polishing profile of a polished surface of a substrate.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side view showing a structure of a polishing apparatus according to a first embodiment of the present invention. The polishing apparatus shown in FIG. 1 comprises a polishing table (turn table) 1 having a circular plate shape. This polishing table 1 is supported by a rotational shaft 3 and arranged so as to rotate in a horizontal plane. A polishing cloth 2 is attached to an upper surface of the polishing table 1 to form a polishing surface 8. A top ring 4 for holding a substrate W is provided above the polishing table 1. This top ring 4 is fixed to a lower end of a top-ring rotational shaft 5, which is supported by a top-ring swing arm 6. This top-ring swing arm 6 swings (rotates) on a swing shaft 7 to allow the top ring 4 to move between a polishing position on the polishing table 1 shown in FIG. 1 and a substrate transfer position (not shown) provided laterally of the polishing table 1. The top ring 4 is moved vertically together with the top-ring rotational shaft 5 with respect to the polishing surface 8 by a non-illustrated vertically moving mechanism, so that the top ring 4 is lowered to press a surface 9, to be polished, of the substrate W against the polishing surface 8 at a predetermined pressure and, on the other hand, the top ring 4 is elevated to move the surface 9 away from the polishing surface 8. A polishing liquid supply nozzle 10, which supplies a polishing liquid (e.g., slurry) onto the polishing surface 8, is provided above the polishing table 1.

This polishing apparatus further comprises a polishing surface temperature controller 20 for providing the polishing surface 8 with a predetermined temperature distribution. This polishing surface temperature controller 20 has a fluid ejection mechanism 30 arranged next to the top ring 4 on the polishing table 1 for ejecting a fluid (a gas in this embodiment) to the polishing surface 8, a temperature-distribution measuring device 40 for measuring a temperature distribution of the polishing surface 8, and a controller 50. Next, these elements of the polishing surface temperature controller 20 will be described in order.

FIGS. 2A and 2B are views illustrating a structure of the fluid ejection mechanism 30. More specifically, FIG. 2A is a view showing the polishing table 1 as viewed from above, and FIG. 2B is a view showing the polishing table 1 as viewed from a lateral direction. In FIG. 2B, only a part of the fluid ejection mechanism 30 is illustrated. FIG. 3 is a view showing a whole structure of the fluid ejection mechanism 30. As shown in FIGS. 2A and 2B, the fluid ejection mechanism 30 is disposed laterally of the top ring 4 on the polishing table 1. Specifically, the fluid ejection mechanism 30 is arranged above portions of the polishing surface 8 which are to move across the surface of the substrate W as the polishing table 1 rotates. The fluid ejection mechanism 30 includes plural (five in the drawings) ejection nozzles (fluid ejection ports) 32 arranged radially so as to surround a side surface of the top ring 4. The ejection nozzles 32 are all directed to the polishing surface 8 and eject a gas toward different portions of the polishing surface 8.

As shown in FIG. 3, the ejection nozzles 32 are coupled to a gas source 34 for supplying a gas, such as a compressed air or nitrogen gas, via pipes 33, respectively, so that the gas is ejected from the gas source 34 through the ejection nozzles 32. Needle valves (i.e., flow rate adjusters) 35 are provided in the pipes 33, respectively, for individually adjusting flow rates of the gas to be ejected through the ejection nozzles 32. Further, flow meters 36 each for measuring the flow rate of the gas are provided respectively on the pipes 33. Measured values from the respective flow meters 36 are sent to the controller 50, so that the respective needle valves 35 are operated by commands from the controller 50.

Temperature adjusters 37 (e.g., heaters or coolers) are provided respectively on the pipes 33 for individually adjusting temperatures of the gas to be ejected through the ejection nozzles 32. The fluid ejection mechanism 30 has supply position adjusters (not shown in the drawings), respectively, for individually changing attitudes of the ejection nozzles 32 so as to adjust supply positions where the ejected gas from the ejection nozzles 32 strikes the polishing surface 8. The temperature adjusters 37 and the supply position adjusters are also operated by commands from the controller 50.

If a dry gas is ejected through the ejection nozzles 32 to the polishing surface 8, this surface 8 would be dried and the slurry would be solidified. As a result, the solidified slurry on the dried polishing surface 8 would scratch the surface 9 of the substrate W. In order to prevent this problem, humidifiers 38 are provided so as to humidify the gas to be ejected through the ejection nozzles 32. Alternatively or additionally, humidifiers or atomizers may be provided near the ejection nozzles 32 so as to prevent drying of the polishing surface 8, although not shown in the drawings.

In this embodiment, the temperature-distribution measuring device 40 comprises a thermography for measuring a temperature distribution of the polishing surface 8 (i.e., a temperature distribution of a portion that comes into contact with the surface 9 to be polished), as shown in FIG. 1. A measurement result of the temperature distribution of the polishing surface 8 by the temperature-distribution measuring device (thermography) 40 is sent to the controller 50. Other than the thermography shown in FIG. 1, a plurality of radiation thermometers for measuring temperatures of portions of the polishing surface 8 may be used as the temperature-distribution measuring device 40.

The controller 50 is electrically connected to both the thermography 40 and the fluid ejection mechanism 30 so as to receive the measurement data from the thermography 40 and send the commands to the fluid ejection mechanism 30. The controller 50 stores polishing profile data of the surface 9 that was measured in advance under a condition that temperature control of the polishing surface 8 was not performed. Further, the controller 50 stores a polishing surface temperature control program 51, which controls the temperature distribution of the polishing surface 8 by automatically determining appropriate flow rates and temperatures of the gas to be ejected through the respective ejection nozzles 32 or by automatically determining the number of ejection nozzles 32 to be used for supplying the gas and supply directions of the ejected gas (i.e., supply positions of the ejected gas).

Next, a polishing operation by the polishing apparatus having the above-mentioned structures will be described. First, the top-ring swing arm 6 is swung to move the top ring 4 to the polishing position on the polishing table 1. Then, the polishing table 1 is rotated about the rotational shaft 3, and the top ring 4 is rotated about the top-ring rotational shaft 5. In this state, the slurry is supplied onto the polishing surface 8 through the polishing liquid supply nozzle 10, and the top ring 4 is lowered by the non-illustrated vertically moving mechanism to press the substrate 9 of the substrate W, which is held on the lower surface of the top ring 4, against the polishing surface 8. In this manner, relative movement between the surface 9 and the polishing surface 8 polishes the surface 9 of the substrate W.

During polishing, the thermography 40 measures the temperature distribution of the polishing surface 8, and sends the measurement data to the controller 50. Based on the measurement data of the temperature distribution and the aforementioned polishing profile data stored in the controller 50, the polishing surface temperature control program 51 calculates a heating or cooling amount of the polishing surface 8 required for providing a uniform removal rate of the surface 9 to thereby determine appropriate flow rates, temperatures, and supply positions of the gas to be ejected through the respective ejection nozzles 32. Further, based on a result of this determination, the controller 50 sends to the fluid ejection mechanism 30 the commands including opening degrees of the respective needle valves 35, target temperatures of the respective temperature adjusters 37, and the target supply positions of the respective supply position adjusters, whereby the ejection nozzles 32 supply the gas at individually adjusted flow rates and temperatures to the adjusted supply positions on the polishing surface 8. With this operation, the polishing surface 8 can be controlled to have a predetermined temperature distribution. Hence, the removal rate of the surface 9 contacting the polishing surface 8 can be uniform, and therefore, the substrate 9 can be planarized.

When adjusting the flow rates of the gas through the respective ejection nozzles 32, one or more needle valves 35 may be completely closed to stop gas supply through the corresponding ejection nozzles 32, so that the number of ejection nozzles 32 for use in gas supply can be adjusted. It is not necessary to control all of the above-mentioned elements including the flow rate, temperature, and supply position of the ejected gas. At least one of them may be controlled to adjust the temperature distribution of the polishing surface 8.

According to the polishing apparatus having the above structures, the polishing surface temperature controller 20 can provide a desirable temperature distribution on the polishing surface 8 contacting the surface 9 to be polished. Hence, even in a CMP process in which the removal rate greatly depends on the temperature of the polishing surface 8, the removal rates of portions of the surface 9 can be controlled as desired. As a result, the pressure applied to the surface 9 in its entirety is not required to be lowered, and hence planarization of the surface 9 can be achieved while maintaining a high removal rate and a good productivity.

As described above, the polishing surface temperature controller 20 has the plural ejection nozzles 32 through which the gas is ejected to different portions of the polishing surface 8, and has mechanisms for individually adjusting the flow rates, temperatures, and supply positions of the ejected gas from the respective ejection nozzles 32. Such structures can divide the polishing surface 8 into small zones as desired, and can control the temperature distribution, i.e., temperatures of the respective zones. Therefore, the removal rates of the portions of the surface 9 can be accurately controlled, and hence the surface 9 can be planarized to a highly flat finish.

The above polishing process may comprise a first-stage polishing process (a first polishing process) and a second-stage polishing process (a second polishing process) so that the flow rate of the gas ejected from the fluid ejection mechanism 30 can be changed in the first-stage and second-stage polishing processes while polishing the substrate W. For example, in the first-stage polishing process, the substrate W is polished while the fluid ejection mechanism 30 ejects the gas therefrom to control the temperature of the polishing surface 8, and in the second-stage polishing process, the substrate W is polished while the fluid ejection mechanism 30 ejects the gas at a lower flow rate than that during the first-stage polishing process or stops supplying the gas (i.e., the polishing surface temperature controller 20 stops controlling of the temperature of the polishing surface 8). Such polishing operations can prevent drying of the polishing liquid on the polishing surface 8 in the second-stage polishing process. Hence, aggregation of abrasive particles can be prevented, and defects, such as scratching of the surface 9 (polishing scratches), can thus be prevented. Similarly, in the first-stage polishing process, the substrate W may be polished while the fluid ejection mechanism 30 ejects a non-humidified gas therefrom, and in the second-stage polishing process, the substrate W may be polished while the fluid ejection mechanism 30 ejects a gas or an atomized fluid (i.e., a mixture of a gas and a liquid) which has been humidified by the humidifier 38, other humidifiers, atomizers, or the like, in order to prevent drying of the polishing liquid on the polishing surface 8.

In the polishing process using the above polishing apparatus, even if the defects, such as scratches, are produced on the surface 9, such substrate is not determined as a defective product so long as a film, to be polished, on the surface 9 is thicker than a depth of the scratch. Accordingly, by dividing the polishing process into the first-stage and second-stage polishing processes and by changing operating conditions of the fluid ejection mechanism 30 in the first-stage and second-stage polishing processes so as to prevent aggregation of the abrasive particles in the second-stage polishing process as described above, it is possible to finally obtain a substrate with no defect, e.g., scratch, on a surface thereof. For this reason, a timing of switching from the first-stage polishing process to the second-stage polishing process is determined based on a size of the aggregation of the abrasive particles. For example, when a thickness of the film reaches 50 nm in the first-stage polishing process, the operation is switched to the second-stage polishing process. This timing of switching is determined based on an output value of a non-illustrated film-thickness measuring device, such as a torque current sensor, an eddy current sensor, or an optical sensor which is provided in the polishing table 1 or the top ring 4.

Alternatively, the timing of switching to the second-stage polishing process may be determined based on time allotment for the first-stage and second-stage polishing processes. For example, the second-stage polishing process can be longer than the first-stage polishing process so that a time of the second-stage polishing process accounts for more than half of the total polishing time. In this case, during the second-stage polishing process, the flow rate of the gas from the fluid ejection mechanism 30 can be lower than that during the first-stage polishing process, or supply of the gas may be stopped during polishing. Alternatively, the gas can be supplied for more than half of the total polishing time, and supply of the gas can be stopped when the polishing process approaches a polishing end point. Although the polishing process is divided into two stages in this example, the polishing process may comprise three or more stages. Further, in the case where the polishing process comprises two stages, an etching process may be performed on the substrate W instead of the second-stage polishing process.

As described above, during the second-stage polishing process, the flow rate of the gas may be lower than that during the first-stage polishing process, or supply of the gas may be stopped. This operation reduces a cooling effect on the polishing surface 8 in the second-stage polishing process, and therefore, the temperature distribution of the polishing surface 8 during the second-stage polishing process becomes higher as a whole than that during the first-stage polishing process. As a result, the removal rate is lowered in the second-stage polishing process. However, because the removal rate is low when polishing is to be finished, the polishing end point can be accurately detected, i.e., the accuracy of the polishing end point detection can be improved. In this manner, polishing can be performed in the second-stage polishing process with the gas being ejected at a low flow rate or without ejection of the gas, so that the temperature distribution of the polishing surface 8 during the second-stage polishing process can be higher than that during the first-stage polishing process. As a result, an ideal polishing end point can be easily and accurately detected.

Next, a second embodiment, of the present invention will be described. In this embodiment, components corresponding to those of the first embodiment will be denoted by the same reference numerals, and will not be described in detail. Further, structures and operations of this and other embodiments, which will not be described below, are identical to those of the first embodiment. FIGS. 4A and 4B are views illustrating a structure of a fluid ejection mechanism 30-2 incorporated in the polishing apparatus according to the second embodiment. More specifically, FIG. 4A is a view showing the polishing table 1 as viewed from above, and FIG. 4B is a view showing the polishing table 1 as viewed from a lateral direction. In FIG. 4B, only a part of the fluid ejection mechanism 30-2 is illustrated. FIG. 5 is a view showing a whole structure of the fluid ejection mechanism 30-2. The polishing apparatus according to this embodiment comprises the fluid ejection mechanism 30-2 shown in FIGS. 4A, 4B and 5, instead of the fluid ejection mechanism 30 incorporated in the polishing apparatus according to the first embodiment.

As shown in FIG. 5, the fluid ejection mechanism 30-2 comprises a blower 43 mounted on one end of a duct 41. This blower 43 is driven by a motor 42. An inlet port 44, having an opening outside the polishing apparatus, is provided on an inlet side of the blower 43. The blower 43 is operated and stopped by commands from the controller 50. An air filter 45 is provided in the duct 41, and an ejection section 46 is provided on another end of the duct 41. As shown in FIGS. 4A and 4B, the ejection section 46 is arranged at a side of the top ring 4 on the polishing table 1 (i.e., arranged at the same position as that of the fluid ejection mechanism 30 of the first embodiment). The ejection section 46 has therein plural (four in the drawing) ejection ports 47, which are arranged radially so as to surround the side surface of the top ring 4. All the ejection ports 47 are directed to the polishing surface 8, so that the gas is ejected through the respective ejection ports 47 to different portions of the polishing surface 8. In the ejection section 46, throttle valves 48 are provided respectively at branching points of the ejection ports 47 from the duct 41. These throttle valves 48 are for individually adjusting opening degrees of paths of the gas to the ejection ports 47, and are operated by commands from the controller 50. Although not illustrated in the drawing, in order to prevent drying of the polishing surface 8, humidifiers may be provided for humidifying the gas ejected through the ejection ports 47, or humidifiers, atomizers, or the like may be provided near the ejection section 46.

In this polishing apparatus, while polishing the surface 9, the blower 43 is operated to suck an air from the outside of the polishing apparatus and supply the air onto the polishing surface 8 to thereby control the temperature distribution of the polishing surface 8. During this operation, as with the first embodiment, the thermography 40 measures the temperature distribution of the polishing surface 8. The polishing surface temperature control program 51 calculates a heating or cooling amount of the polishing surface 8 required for providing a uniform removal rate of the surface 9 based on a measurement result from the thermography 40 to determine appropriate flow rates of the gas to be ejected through the respective ejection ports 47. Then, based on a result of this determination, the controller 50 sends commands including opening degrees of the respective throttle valves 48 to change the opening degrees of the path of the gas to the ejection ports 47, whereby the ejection ports 47 supply the gas at individually adjusted flow rates. With this operation, the polishing surface 8 can be controlled to have a desired temperature distribution. In this case also, it is possible to adjust the number of ejection ports 47 to be used for gas supply by closing one or more throttle valves 48.

FIGS. 6A and 6B are views illustrating a structure of the polishing apparatus according to a third embodiment of the present invention. More specifically, FIG. 6A is a view showing the polishing table 1 as viewed from above, and FIG. 6B is a view showing the polishing table 1 as viewed from a lateral direction. The polishing apparatus according to this embodiment comprises, instead of the fluid ejection mechanism 30 of the first embodiment, a temperature adjustment roller 60 as a mechanism for controlling the temperature distribution of the polishing surface 8. This temperature adjustment roller 60 has a contact section 61 of a substantially conical shape, which is to rotate about a rotational shaft 62 with its side surface 61 a being in rolling contact with the polishing surface 8 that moves with the rotation of the polishing table 1. The contact section 61 is made of metal, such as stainless steel, titanium, or corrosion-resistant aluminum alloy. The side surface 61 a of the contact section 61 comprises plural parts which are made of different kinds of metals having different heat absorptivity so that the contact section 61 can provide a predetermined temperature distribution on the polishing surface 8. Although not shown in the drawings, an elevating mechanism is provided for elevating and lowering the temperature adjustment roller 60 to bring the side surface 61 a of the contact section 61 into and out of contact with the polishing surface 8. This elevating mechanism is operated by command from the controller 50.

In this polishing apparatus, while polishing the surface 9, the temperature adjustment roller 60 is in rolling contact with the polishing surface 8 to perform heat exchange between each part of the side surface 61 a of the contact section 61 and each zone of the polishing surface 8 to thereby control the temperature distribution of the polishing surface 8. During this operation, as with the first embodiment, the thermography 40 measures the temperature distribution of the polishing surface 8. The polishing surface temperature control program 51 calculates a heating or cooling amount of the polishing surface 8 required for providing a uniform removal rate of the surface 9 based on a measurement result from the thermography 40. Then, based on a result of this determination, the temperature adjustment roller 60 is elevated or lowered to adjust a time of contact between the contact section 61 and the polishing surface 8 to thereby provide a desired temperature distribution on the polishing surface 8.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of claims for patent, and the scope of the technical concept described in the specification and drawings. Any shape, structure, and material, which are not specifically described in the specification and the drawings, may be used within the scope of the technical concept, so long as those exhibit the same effect and function as the present invention. For example, a fluid to be supplied from the fluid ejection mechanism 30 is not limited to a gas, and a liquid or an atomized fluid (i.e., a mixture of a gas and a liquid) may be used. A gas is not limited to the aforementioned compressed air or a nitrogen gas, and other types of gases can be selected according to the purpose. Further, the number and the shape of ejection nozzle 32 and ejection port 47 of the fluid ejection mechanism are not limited to those of the embodiments described above, and any number and shape can be employed so long as they can provide a desired temperature distribution of the polishing surface 8. In addition, specific structures of the polishing apparatus are not limited to those described in the embodiments.

EXPERIMENTAL EXAMPLE

Next, an experimental example of the present invention will be described with reference to FIGS. 7A and 7B. FIG. 7A is a view showing the polishing table 1 as viewed from above, and FIG. 7B is a graph showing a polishing profile of the polished surface of the substrate W. More specifically, FIG. 7B shows comparison of the polishing profile between a case where the polishing surface 8 was not heated or cooled (i.e., the temperature distribution of the polishing surface 8 was not adjusted) during polishing and a case where predetermined portions (indicated by symbol “A” in FIG. 7A) of the polishing surface 8 were cooled during polishing.

Cooling of the polishing surface 8 was performed by ejecting the gas only from the ejection nozzles 32 that are arranged at locations corresponding to the portions A of the polishing surface 8 of the polishing apparatus according to the above embodiment. In FIG. 7B, a horizontal axis shows measurement position on the surface 9 (indicated by a distance from a center of the surface 9), and a vertical axis shows removal rate. As can be seen from the polishing profile shown in the graph, in the case where polishing was performed without controlling the temperature distribution of the polishing surface 8, the removal rate was lower at a point closer to the peripheral edge of the surface 9 as a result of a distribution of pressure applied to the surface 9. On the other hand, in the case where polishing was performed while controlling the temperature distribution of the polishing surface 8, i.e., while cooling the portions of the polishing surface 8 which came into contact with the peripheral edge and its nearby portions of the surface 9, the removal rate of the portions including the peripheral edge of the surface 9 was increased. As a result, a uniform removal rate was obtained over the surface 9 in its entirety, and hence the surface 9 was planarized. 

1-14. (canceled)
 15. A method of polishing a substrate whose characteristic is such that a removal rate thereof increases as a polishing temperature decreases, said method comprising: performing a first polishing process of polishing a surface of the substrate by providing sliding contact between the surface of the substrate and a polishing surface while supplying a polishing liquid onto the polishing surface; during said first polishing process, ejecting a fluid to the polishing surface to cool the polishing surface; and performing a second polishing process of polishing the surface of the substrate by providing sliding contact between the surface of the substrate and the polishing surface while supplying the polishing liquid onto the polishing surface, said second polishing process being performed without ejecting the fluid to the polishing surface so as to maintain a temperature of the polishing surface higher than that during said first polishing process.
 16. The method according to claim 15, wherein said fluid is a gas.
 17. The method according to claim 15, wherein said fluid is a mixture of a gas and a liquid.
 18. A method of polishing a substrate whose characteristic is such that a removal rate thereof increases as a polishing temperature decreases, said method comprising: performing a first polishing process of polishing a surface of the substrate by providing sliding contact between the surface of the substrate and a polishing surface while supplying a polishing liquid onto the polishing surface; during said first polishing process, ejecting a fluid to the polishing surface at a first flow rate to cool the polishing surface; performing a second polishing process of polishing the surface of the substrate by providing sliding contact between the surface of the substrate and the polishing surface while supplying the polishing liquid onto the polishing surface; and during said second polishing process, ejecting the fluid to the polishing surface at a second flow rate that is lower than the first flow rate so as to maintain a temperature of the polishing surface higher than that during said first polishing process.
 19. The method according to claim 18, wherein said fluid is a gas.
 20. The method according to claim 18, wherein said fluid is a mixture of a gas and a liquid. 